Microprocessors are coming into increasing widespread use in many products. They are presently being used in such diverse products as calculators, microwave ovens, and automatic dialing telephones. In addition, microprocessors presently available are low power devices and therefore can be powered off of either a battery or commercial power. However, in order to extend battery life when batteries are used and to conserve energy when commercial power is used, it is highly desirable that power not be applied to the processor when it is not operating.
One common approach to dealing with this problem is to apply power to and remove power from the processor by an on/off switch. The drawback of this solution is that the user may become distracted and forget to turn the power off. Furthermore, for some users, the processor is operated on an intermittent basis. It then becomes inconvenient, if not a nuisance, to be constantly using the on/off switch to apply power to and remove power from the processor.
This problem of extending battery life and conserving energy becomes even more difficult and also more important when the processor operates in conjunction with a volatile memory in which information is stored that needs to be retained between operations of the processor. Power then needs to be continuously applied to the memory.